This disclosure relates to internal combustion engines and selective catalytic reduction (SCR) after-treatment systems for such engines. SCR systems are for reducing NOx that are generated in internal combustion engines.
The SCR systems involve the chemical reduction of NOx in the presence of a catalyst. SCR catalysts are manufactured from various ceramic materials used as a carrier, such as titanium oxide, and active catalytic components may be oxides of base metals (such as vanadium, molybdenum and tungsten), zeolites, or various precious metals. The catalyst operates more efficiently at temperatures much warmer than ambient. Systems warm up through passing exhaust gases from an engine thru upstream after-treatment components such as diesel oxidation catalyst (DOC) and diesel particulate filter (DPF), although there is heat loss as the exhaust passes thru upstream components delaying the warm up of the SCR catalyst and hence delaying efficient reduction of NOx.
One technique to allow for faster warm up of the SCR catalyst is to add insulation to the selective catalytic reduction (SCR) converter or container to reduce heat loss.